In many cardiac procedures, it is necessary to obtain access through the cardiac septum. For example, in treating atrial fibrillation, it is often necessary to isolate the electrical pathways from the PVs (“PVs”), which are located on the posterior wall of the left atrium (“LA”). As all other veins from the body lead to the right atrium, in order to get to the LA, catheters must get across the atrial septum. This is done by piercing a small hole in the septal wall, typically at a location called the fossa ovalis (“FO”). Such access is termed transseptal (“TS”) access. Once in the LA, the physician may perform a procedure to electrically isolate the PVs from the LA.
In more detail, TS access is performed by delivering a sheath/dilator thru the venous bed into the right atria along the septal wall. With the tip of the dilator dragged along the septal wall, the same is dragged to the location of the FO. The sheath is then slightly advanced forward, applying pressure to the FO, creating what is called “tenting” of the FO. A long TS needle (e.g., a “Brockenbrough” or “BB” needle) is then advanced thru the lumen of the dilator that is inserted thru the sheath. The needle is advanced against the FO while it is tented. The needle then punctures thru the FO and into the LA.
The TS needle may be hollow or may incorporate a guidewire lumen to enable a guidewire to be threaded through and into the LA of the heart. Once the guidewire is passed through the TS needle and into the LA, the needle, dilator and sheath are retracted while the guidewire remains in the LA.
In about 20% of TS cases, there is difficulty obtaining TS access because, as the physician pushes the sheath forward with the needle, both slide up or down instead of moving forward, increasing the tension on the FO, causing the same to tent while the needle penetrates the tissue. In other cases, if the septum is heavily fibrotic, significant pressure is required to advance the TS needle into the LA. Both cases occasionally cause puncture of the opposite wall by a sudden exertion of the needle through the septum and subsequent perforation, causing a severe adverse event and potential for death.